Toothbrushes conventionally have bristles of equal length, both along and across the face of the handle. Teeth on the other hand geernally have curved surfaces. Owing to this lack of conformity between the bristle contour and that of the teeth, contact pressure, and hence cleaning effectiveness is nonuniform. Such nonuniformity of cleaning is especially problematic in the region of the molars, where food particles tend to become lodged because of the high crushing pressures and where the surfaces cannot readily be inspected to ascertain the extent to which they have been cleaned. In addition to these deficiencies related to cleaning effectiveness, toothbrushes of the prior art generally have handles of rectangular cross-section and, as a result, are difficult to grip.
Various toothbrushes of the prior art have specially shaped bristles for facilitating the cleaning of various parts of the teeth and adjacent gums, as well as specially designed handles for improved grip. Such toothbrushes are shown, for example, in Davenport U.S. Pat. No. 803,995, Kuzzer U.S. Pat. No. 890,143, Malcolm U.S. Pat. No. 2,043,898, Olson U.S. Pat. No. 2,797,424, Smith U.S. Pat No. 3,792,504, Kim U.S. Pat. No. 3,934,298, Warren et al U.S. Pat. No. 4,033,008, Booth U.S. Pat. No. 4,330,896 and Rauch U.S. Pat. No. 4,610,045. None of these toothbrushes, however, have completely solved the problems referred to above.